The present invention relates to a catalyst for the hydroformylation of at least one olefin, a method for using of such a catalyst and a method for the hydroformylation of olefins.
Hydroformylation is an important industrial process in which an olefin or alkene is converted with carbon monoxide and hydrogen (synthesis gas) to an aldehyde. The total volume of aldehydes produced by hydroformylation currently averages over 10 million tons per year.
For the majority of the alkenes, several products can be formed depending on the regioselectivity of the addition reaction. The linear and branched product are generally obtained as a mixture, wherein the linear product is preferred for industrial applications. The primarily occurring aldehydes are usually hydrogenated to alcohols, which are used as plasticizers for PVC or as solvents, or are further processed into polymers.
There are currently two main methods for the hydroformylation of alkenes. One method involves the use of a cobalt catalyst, which in general is used for the production of higher aldehydes and alcohols with a chain length of C>5. As separation of the homogenous catalyst is difficult in the case of medium- or long-chain olefins, cobalt catalysts, which are cheaper compared to rhodium, are used in this case.
In contrast, ligand-modified rhodium catalysts are used for short-chain olefins, as in this case the catalyst complex can be quantitatively separated (e.g. the Ruhrchemie/Rhône-Poulenc method). Rhodium-catalyzed hydroformylation reactions are carried out under relatively mild conditions and are generally used for the hydroformylation of ethene and propene, but also for the conversion of 2-propen-1-ol to butane diol.
There is a need for more selective and active catalysts for the formation of aldehydes that can also be used for higher aldehydes. Ligands used in catalyst complexes are of special importance for increasing the activity and selectivity of hydroformylation.
The selection of a suitable ligand is of decisive importance for the activity and selectivity of hydroformylation. Accordingly, research is focused on the synthesis and coordination chemistry of new ligands. It is advantageous that the number of different ligands for use in hydroformylation is virtually infinite. Up to now, phosphorus, nitrogen, or carbene ligands have chiefly been used for hydroformylation, in particular for rhodium-catalyzed hydroformylation. Phosphines, with three alkyl groups bonded to the phosphorus atom, and phosphites, with three alkoxy groups bonded to the phosphorus atom, are of considerable interest, wherein catalysts modified with phosphites often show stronger activity. The steric properties of the ligands are also a critical parameter with respect to the regioselectivity of hydroformylation.
Because of the major economic significance of hydroformylation, however, there is still a need for catalysts that show both improved activity and improved regioselectivity.